Chapter 8 

 THE DEUTEROMYCETES (FUNGI IMPERFECTI) 



The Deuteromvcetes are in reality the trash pile or the left- 

 overs, containing the conidial- or imperfect-stage remnants of the 

 classes already discussed. In many ways they are of the greatest 

 interest among all the classes of fungi and certainly are of time- 

 consuming concern to the mycologist in his taxonomic prob- 

 lems. They are not given extended treatment in texts mainly 

 for the reason that the groupings are wholly artificial and hence 

 are completelv without phvlogenetic significance. 



To date between 15,000 and 20,000 Fungi Imperfecti have 

 been described. According to Bender (1931), this vast miscel- 

 laneous assemblage represents 1331 form genera. They com- 

 prise (1) the mycelial, sclerotial, and conidial stages of species 

 having perfect stages, that is, zygospores, oospores, asci, basidia, 

 and teliospores, and therefore properly belong in the classes 

 already discussed, and (2) those species of fungi whose perfect 

 stages are not known. Even though the zygospores or oosporic 

 stages of certain Phvcomycetes have never been observed, these 

 species are commonly placed among the Phycomycetes rather 

 than among the Deuteromycetes because of the coenocytic na- 

 ture of their assimilatory structures. Furthermore, many rusts 

 are known only in the aecial or uredinial stage but are properly 

 placed in the Uredinales among the imperfect form genera 

 Aecidium, Peridermium, Caeoma, Roestelia, and Uredo. Since 

 the hyphae of many Basidiomycetes possess clamp connections, 

 this criterion is of value, in the absence of a basidial stage, in 

 relating so-called imperfect fungi to the Basidiomycetes. It seems 

 probable therefore that the great majority of species treated as 

 Fungi Imiperfecti really are Ascomycetes whose connection with 

 an ascogenous stage has not been established. Some may never 

 have possessed a perfect stage or, if they did, may have lost it. 



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